The present invention relates to a method and an apparatus for automatically tuning a pre-pit slicing level.
According to the DVD-RW specification as an example, the optical storage device generates a plurality of pre-pit signals when reading the optical storage disc. The pre-pit signals correspond to physical addresses of the optical storage disc. Levels of the pre-pit signals vary due to the variance of discs, number of access times, and system states of the optical storage device. Whether the levels can be correctly detected influences the performance of the optical storage device.
FIG. 1 illustrates a diagram of a pre-pit slicing level PPSLV according to the related art. The pre-pit slicing level PPSLV is generated utilizing a signal source of a fixed level. That is, the pre-pit slicing level PPSLV is fixed. Please note that the levels of pre-pit signals 110p, 120p, and 130p are not identical. In addition, amplitudes of different waveforms 110, 120, and 130 where the pre-pit signals 110p, 120p, and 130p are respectively located are usually different. Furthermore, some of the waveforms 110, 120, and 130 vary with different offsets. As a result, using the pre-pit slicing level PPSLV having a fixed level to slice the pre-pit signals 110p, 120p, and 130p would lead to erroneous identification of the physical addresses to which the pre-pit signals 110p, 120p, and 130p correspond. An ideal case shown in FIG. 1 involves the pre-pit slicing level PPSLV crossing the pre-pit signal 110p so that the physical address to which the pre-pit signal 110p corresponds can be correctly identified. An erroneous case shown in FIG. 1 can be seen when the pre-pit slicing level PPSLV does not cross the pre-pit signal 120p so that the physical address to which the pre-pit signal 120p corresponds cannot be identified. Another erroneous case shown in FIG. 1 can be seen when the pre-pit slicing level PPSLV crosses the waveform 130 under the pre-pit signal 130p so that the physical address to which the pre-pit signal 130p corresponds would be inaccurately identified. In addition, the pre-pit slicing level PPSLV further crosses the waveform 130w so that the physical address to which the pre-pit signal 130p corresponds will be erroneously identified.